If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Hi Marko
The UC3710s are CMOS with MOSFET output stages, and like all CMOS chips they have parasitic diodes from every pin to the supply rails, and though we call them "diodes" they are actually part of a parasitic thyristor. Putting enough current through any parasitic diode will fire the thyristor and short the supply rails together, and voila latchup.
These parasitic diodes are in parallel with the clamp diodes you add. So your diodes have to conduct with a lower forward voltage if they're to succeed in diverting the current away. This is why they have to be Schottkies.
UCCs have a guaranteed latchup-free current through the clamp diodes, but it's quite possible to exceed this if you screw up the GDT design or get a primary strike.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi Steve, thanks :)
The UC3710s are CMOS with MOSFET output stages, and like all CMOS chips they have parasitic diodes from every pin to the supply rails, and though we call them "diodes" they are actually part of a parasitic thyristor. Putting enough current through any parasitic diode will fire the thyristor and short the supply rails together, and voila latchup.
Steve, the output stages are bipolar - I posted the datasheet in first post. There is a schematic showing the output stage and they claim in the text that it is a bipolar totem pole. If they are mos datasheet would have to be complete BS.
And this 'latchup' isn't really hazardous, output just goes low and devices heat a bit more. Even when they are alright they are warm, apparently because of output stage bias.
And if that is true, why do they keep latching up even with schottky diodes right on their terminals? And only when I put the circuit into the big coil (8 IRFP450's, 2 fullbridges with 2 primaries, 8 isolated GDT secondaries), they work completely fine with halfbridge giving 16cm full wave sparks.
I'm pretty sure they latch up, since ping signal I always get from NE555 disappears from the output.
It's only me who can create this much trouble from a simplest circuit in the world. I'm truly special
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Forgot to mention one thing, interestingly, the drivers seem to measure 600mV drop backwards from output to supply, just like if they had diodes... But I don't know how could any harm happen with schottky diode bypass.
It's all starting to look like my paralleled H bridges are messing something, but I can't really find a mistake. I'm sort of spinning in circles for 2 months now with this, most unsuccessful SSTC ever.
I'm having a shipment of IXDD414's arriving these days, I'll see what can I do with them. Thanks guys, for replies, I bothered you enough.
I can post the schematic of the current circuit if anyone wishes...
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
Just thought I'd give an update on the issue.
I recently made an SLR inverter for charging HV caps, and experienced a sudden loss of output from the driver. This would happen at higher supply voltages first, but I was able to circumvent it by shielding the driver. Having thought this solved the issue I later attempted to charge capacitors only to find the problem was still there. After some googling this weekend I found this thread and this blog post , which pinned down the issue. I replaced the UC3710s with a pair of good ol' UCC3732x drivers and the problem is gone. I wouldn't recommend anyone to use UC3710 gate drivers for driving GDTs anymore.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
UC3710 gate drivers keep turning off.
